Links between processed meat and colorectal cancer

WHO statement
29 October 2015

WHO has received a number of queries, expressions of concern and requests for clarification following the publication of a report from the International Agency for Research on Cancer (IARC) relating to processed meat and colorectal cancer.
IARC was established 50 years ago through a resolution of the World Health Assembly as a functionally independent cancer agency under the auspices of WHO. Its programme of work is approved and financed by its participating states.
IARC’s review confirms the recommendation in WHO’s 2002 “Diet, nutrition and the prevention of chronic diseases” report, which advised people to moderate consumption of preserved meat to reduce the risk of cancer. The latest IARC review does not ask people to stop eating processed meats but indicates that reducing consumption of these products can reduce the risk of colorectal cancer.
WHO has a standing group of experts who regularly evaluate the links between diet and disease. Early next year they will meet to begin looking at the public health implications of the latest science and the place of processed meat and red meat within the context of an overall healthy diet.For more information, please contact:

Moderation is key when weighing cancer risk of meat
LESLIE BECK
Special to The Globe and Mail
Last updated Monday, Nov. 02, 2015 3:18PM EST

Last week’s headlines tying some types of meat to colorectal cancer left many people wondering whether they should banish them from their diet altogether.

Is it finally time to give up that juicy steak? Should you trade in cold cuts for tuna?

To recap, the International Agency for Research on Cancer (IARC), a subsidiary of the World Health Organization, ruled that processed meat causes colorectal cancer and red meat (e.g., beef, pork, lamb, goat) probably does.

The term “processed meat” refers to meats preserved by smoking, curing, salting or adding preservatives.

So are turkey (and chicken) sausages, smoked turkey and turkey bacon. However, most studies have looked only at processed red meats.

While the IARC’s conclusion means there is an established and scientifically valid association between red and processed meats and the risk of cancer, there’s no need to panic.

Just because something raises the risk of cancer doesn’t mean it will cause cancer.

Dose matters – how much meat you eat, how often you eat it and for how long you’ve been eating it. And, it’s important to note, other dietary and lifestyle choices will affect the risk, too.

You don’t have to stop eating red meat. It is a good source of high-quality protein, B vitamins, iron and zinc. That said, if you eat red meat frequently and in large portions, you should cut back.

Based on an expert review of 7,000 studies that was published in 2007, the American Institute for Cancer Research advises eating no more than 18 ounces (500 grams) of red meat each week. The Canadian Cancer Society recommends a stricter limit of three servings – three ounces each – per week.

Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto.

A new report classifying processed meats such as hot dogs and bacon as “carcinogenic” to humans doesn’t set out a cause-and-effect link between meats and cancer, industry groups caution.
The International Agency for Research on Cancer (IARC), a research arm of the World Health Organization, on Monday published a report placing processed meats in its Group 1 category, which includes substances such as tobacco and asbestos with “sufficient evidence” of links to cancer.
The IARC on Monday also put red meat, such as beef, pork and lamb, in its Group 2A — where glyphosate, the active ingredient in Roundup herbicide, was recently also classified as a “probable” carcinogen. (The IARC’s Group 2B, of “possible” carcinogens, recently saw 2,4-D herbicide added to the list.)
In its response Monday to the report, the Canadian Meat Council emphasized that the IARC defines an agent that “may cause cancer at some level, under some circumstance,” as a “cancer hazard.”
However, the CMC said, actual “cancer risk” gauges the likelihood of experiencing cancer after being exposed to a “cancer hazard,” and the IARC identifies such hazards even when the risks are “very low.”
Such findings aren’t unusual for the IARC, the Canadian Cattlemen’s Association said in a separate release, saying the agency “has found hazards in about half of the agents it has reviewed.”
For its 2A classification for red meat, the CCA said, the IARC’s review of existing epidemiological studies “concluded that there is limited evidence in human beings for the carcinogenicity of the consumption of red meat,” and “no clear association was seen in several of the high quality studies and residual confounding from other diet and lifestyle risk is difficult to exclude.”
Colorectal cancer was the IARC report’s “principal focus” relative to red meat, the CCA said. The report had cited 10 cohort studies with a “statistically significant dose–response relationship,” with a 17 per cent increased risk per 100 grams per day of red meat.
Given that the American Society of Clinical Oncology (has estimated a person with an “average” risk of colorectal cancer has about a five per cent chance of developing colorectal cancer overall, consuming 100 g per day of red meat would increase the risk of colorectal cancer by just under one per cent in absolute terms, the CCA said.
The meat industry has previously estimated Canadians, on average, eat only about 50 g of fresh red meat per day. Thus, the CCA said, “if there is an increase in the potential risk of colorectal cancer from red meat consumption, by these estimates it is small and must be considered relative to the very significant nutritional benefits that red meat provides.”
“It is regrettable that, in arriving at its split decision, the IARC panel reportedly chose to disregard certain studies which present high quality evidence to the contrary,” CMC president Joe Reda said.
“Furthermore, the agency did not balance its verdict by taking into account either the proven benefits of meat or the substantive implications of removing meat from the diet… Risks and benefits should both be considered before recommending what people eat and drink.” — AGCanada.com Network

Bacon causes cancer and a New York strip steak probably does too. On Monday, the World Health Organization’s International Agency for Research on Cancer announced that processed meat is carcinogenic and that red meat, including beef, veal, pork and lamb, probably causes cancer. The announcement has many rethinking what they eat and whether they can ever enjoy a guilt-free hot dog or hamburger again. It’s critical to look beyond the headlines to answer those questions.

What happened?

The IARC decided to study processed and red meat on the advice of an international advisory committee that highlighted the mounting evidence linking both to cancer. This month, 22 scientists from 10 countries met in Lyon, France, to figure out once and for all what those risks are.

The group looked at more than 800 studies from around the globe. The relationship between meat and colorectal cancer was the most widely studied. In their assessment, the researchers gave the most weight to prospective studies – ones that followed a group of participants for a period of time to track their health outcomes.

After reviewing all of the information, the working group concluded that there is enough evidence to classify processed meat as carcinogenic. Processed meat refers to meat that has been cured, smoked, salted or otherwise processed to increase flavour and shelf life: anything from bacon to ham to lunch meat to pepperoni.

Specifically, the group ruled that processed meat increases the risk of colorectal cancer. A person who consumes 50 grams of processed meat a day (roughly equivalent to a hot dog, two pieces of bacon or a few slices of smoked turkey) has an 18 per cent increased risk of developing that type of cancer.

The story was slightly different with red meat. The working group found that while there is evidence that red-meat consumption raises the risk of colorectal cancer, the currently available data are not sufficient to definitively declare red meat as carcinogenic. The group also pointed out that some studies have found that red meat may increase the incidence of pancreatic and prostate cancer.

Although red meat, such as beef, pork and lamb, contains important vitamins and nutrients, the IARC said consumption leads to the formation of N-nitroso compounds, which are carcinogenic, in the colon. Cooking meat can also produce certain carcinogenic chemicals.

More study is needed to figure out the exact underpinnings of the relationship between meat and cancer, but enough evidence is in to determine that it is a risk.

Does this mean processed meat carries the same risk as tobacco?

It is incorrect and misleading to equate the dangers of smoking and processed meat. What they now have in common is that they are both in Group 1, IARC’s list of known carcinogens. Group 1 carcinogens are those for which the evidence clearly shows that they cause cancer. Red meat belongs to Group 2A because there is limited evidence that it probably causes cancer.

The risks associated with tobacco products are much greater than processed meat, however. The Global Burden of Disease Project estimates that 34,000 people die of cancer every year as a result of consuming processed meat. Compare that with the more than one million people who die from cancer worldwide annually as a result of tobacco. Not to mention the millions of others who die as a result of tobacco-induced respiratory diseases, heart disease and other problems.

So now do I have to break up with bacon and steak?

Not necessarily. Declaring that something is carcinogenic lets people know that it poses a risk. It doesn’t mean we should banish the item in question. As the American Cancer Society points out, there are plenty of cancer-causing substances that are unavoidable, such as radiation, to which we are exposed through the soil as well as X-rays and other medical procedures, as well as estrogen, which occurs naturally in the human body.

Another known carcinogen on the IARC’s Group 1 list? Wood dust. Of course, that doesn’t mean anyone who has ever walked through a lumberyard or endured a major home renovation is going to develop a disease as a result.

The key is finding a balance of how to manage potential risks, says Sian Bevan, director of research at the Canadian Cancer Society. “It’s important to remember it’s a relative risk,” she said. “An individual’s personal risk [for colorectal cancer] is already relatively low.”

Cancer Research UK, a London-based charity, crunched the numbers to provide some much-needed perspective. According to the organization, 61 out of every 1,000 people in the United Kingdom will develop colorectal cancer during their lives. For those that eat the least amount of processed meat, that number is 56 out of 1,000. Using the results of a study conducted in 2011 by the World Cancer Research Fund, the rate for people who consumed the highest amount of processed meat is 66 out of 1,000. In other words, eating a diet rich in bacon, ham, salami and other processed meats does pose a higher risk, but it isn’t the equivalent of a cancer diagnosis.

What about “natural” processed meats?

You’ve probably seen a new crop of hot dogs and bacon in your grocery store with the word “natural” emblazoned on the packaging. According to the labels, those types of products are made using such easy-to-pronounce ingredients as sea salt, vinegar and cultured celery extract. However, that doesn’t mean those products have a lower cancer risk or are otherwise healthier. The “natural” preservatives are still a source of nitrates and nitrites, compounds that have been linked to an increased cancer risk.

Cancer isn’t the only concern

Keep in mind that cancer is just one negative health outcome. Choosing salty, fatty, highly processed meat products can also raise the risk of high blood pressure, obesity, cardiovascular disease and a host of other health issues.

That’s why groups such as the Canadian Cancer Society are preaching moderation – sure, you can enjoy a nice steak dinner, but don’t forget about fruits, vegetables, fish and grains.

So what might a moderate balanced diet look like? The society recommends people limit their consumption of red meat to three times a week and to reserve processed meat for special occasions.